Heavy oil catalytic cracking catalyst and preparation method therefor

ABSTRACT

The present invention relates to a heavy oil catalytic cracking catalyst and preparation method thereof. The catalyst comprises 2 to 50% by weight of an ultra-stable rare earth type Y molecular sieve, 0.5 to 30% by weight of one or more other molecular sieves, 0.5 to 70% by weight of clay, 1.0 to 65% by weight of high-temperature-resistant inorganic oxides, and 0.01 to 12.5% by weight of rare earth oxide. The ultra-stable rare earth type Y molecular sieve is obtained as follows: the raw material, NaY molecular sieve, is subjected to a rare earth exchange and a dispersing pre-exchange, and the molecular sieve slurry is filtered, washed and subjected to a first calcination to produce a “one-exchange one-calcination” rare earth sodium Y molecular sieve, wherein the order of the rare earth exchange and the dispersing pre-exchange is not limited; and the “one-exchange one-calcination” rare earth sodium Y molecular sieve is further subjected to ammonium salt exchange for sodium reduction and a second calcination. The catalyst provided in the present invention is characteristic in its high heavy-oil-conversion capacity, a high total liquid yield and a high light oil yield.

FIELD OF TECHNOLOGY

The present invention relates to a heavy oil catalytic cracking catalysthaving a high heavy-oil-conversion capacity and the preparation methodthereof, and more particularly, to a catalytic cracking catalystsuitable for residual oil blending and the preparation method thereof.

BACKGROUND ART

Catalytic cracking apparatuses are crucial means for crude oil refining,and the economic benefits of refineries depend on the overall productdistribution of these apparatuses. Recently, because of the growingtrend towards crude oils having higher density and poorer quality, ahigher heavy oil conversion capacity and higher selectivity forhigh-value products are demanded for FCC catalysts. The type Y molecularsieve has been a major provider of the cracking activity of heavy oilcatalytic cracking catalysts, and its activity stability and crackingactivity are key factors in determining the heavy oil conversioncapacity of FCC catalysts.

Accordingly, extensive investigations have been carried out in domesticand abroad research institutions in order to improve the crackingactivity and activity stability of type Y molecular sieves. Currently,it is largely agreed that the framework structural stability and theactivity stability of molecular sieves can be improved by localizing asmany rare earth ions as possible in sodalite cages in the process ofrare earth modification of molecular sieves so as to suppressdealumination of the molecular sieve framework during steam aging.Patent ZL200410058089.3 describes a method for preparing rareearth-modified type Y molecular sieves, comprising steps of adjustingthe pH of the system to 8-11 using an alkali solution after completionof a rare earth exchange reaction, and then carrying out conventionalsubsequent treatment processes. In the molecular sieves prepared by thismethod, rare earth ions are completely located in small cages (sodalitecages). Patent ZL200410058090.6 describes the reaction performance ofthe molecular sieves of ZL200410058089.3, wherein the catalyst reactionresults show that localization of rare earth metals in sodalite cagesimproves the structural stability and the activity stability of themolecular sieves, manifested in that the heavy oil conversion capacityof the catalyst is greatly improved, although this catalyst has poorcoke selectivity.

Chinese patent ZL97122039.5 describes a preparation method forultra-stable Y zeolites, comprising steps of putting a Y zeolite intocontact with an acid solution and an ammonium-containing solution, andsubjecting them to a high-temperature steam treatment, wherein theamount of the acid used is 1.5 to 6 moles of hydrogen ions per mole offramework aluminum, the concentration of the acid solution is 0.1 to 5N, the Y zeolite is kept in contact with the acid solution at atemperature of 5 to 100° C. for a duration of 0.5 to 72 h, and theweight ratio between the Y zeolite and the ammonium ion is 2 to 20. Themodification method in accordance with this patent requires addition ofan ammonium-containing solution for the purpose of lowering the sodiumoxide content in the molecular sieve or reducing the damage to themolecular sieve structure caused by acidic gases during calcination. TheFCC catalyst prepared using such molecular sieves is characteristic inits high capacity of heavy oil conversion and a high light-oil yield.However, this modification technique for molecular sieves have thefollowing technical disadvantages: 1) since a large number of ammoniumions are added in the preparation process, ammonium-containing ionseventually enter the atmosphere or waste water, increasing ammonianitrogen pollution and the cost for pollution control; 2) the method ofthis patent is unable to solve the issue of particle agglomeration inmolecular sieves, which issue reduces specific surface area and porevolume of the molecular sieve and increases the obstruction in the porechannel during exchange in the molecular sieve, making it difficult toaccurately and quantitatively localize the modifying element in thecages of the molecular sieve; 3) moreover, in this patent it is furthermentioned that rare earth ions may also be introduced by ion exchange,during or after the contact between the Y zeolite and theammonium-containing solution, and that during the ion exchange, ammoniumions compete with rare earth ions and preferentially take up thepositions intended for rare earth ions, thereby hindering rare earthions from entering the cages of the molecular sieve by exchange, andalso lowering the utilization of rare earth ions.

Chinese patent ZL02103909.7 describes a method for preparing rareearth-containing ultra-stable Y molecular sieves by subjecting a NaYmolecular sieve to one exchange process and one calcination process,characterized in that the NaY molecular sieve is placed in an ammoniumsolution and subjected to chemical dealumination at 25 to 100° C. for0.5 to 5 h, wherein the chemical dealumination chelating agent containsoxalic acid and/or oxalate salts, a rare earth solution is thenintroduced under stirring to produce a rare earth precipitate thatcontains rare earth oxalate, and the precipitate is filtered and washedto give a filter cake, followed by a hydrothermal treatment to affordthe molecular sieve product. Although the molecular sieve prepared bythis method has certain resistance to vanadium contamination, it hasrelatively low activity stability and cracking activity, and isinsufficient to meet the requirement set out by the growing trendtowards crude oils having higher density and poorer quality. This issueis mainly attributed to the distribution of rare earth ions in thesuper-cages and sodalite cages of the molecular sieve duringmodification. This method demonstrates that rare earth ions are presentin the molecular sieve system in two forms, i.e., a part of the rareearth enters sodalite cages in an ionic form while the other part isscattered over the surface of the molecular sieve as an independentphase of rare earth oxide (the precursor of which is rare earth oxalateand is converted into rare earth oxide after subsequent calcination).Such distribution reduces the stabilizing and supporting effect of rareearth ions on the molecular sieve structure. Furthermore, this methodalso poses a remarkable problem of ammonium nitrogen pollution, and theoxalic acid or oxalate salts added are also toxic and detrimental to theenvironment and human.

CN200410029875.0 discloses a preparation method for rare earthultra-stable type Y zeolite, characterized by a step of treating zeolitewith a mixed solution comprising a rare earth salt and citric acid orwith a mixed solution comprising an inorganic ammonium salt, a rareearth salt and citric acid. This method simplifies the process, and thezeolite prepared thereby, when serving as an active component of acracking catalyst, is advantageous in lowering the olefin content ingasoline products obtained from the catalytic cracking, andsubstantially increasing the yield of light oil products obtained fromthe catalytic cracking. However, this method does not specify thelocation of rare earth ions in the molecular sieve.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a new catalyticcracking catalyst with high heavy-oil-conversion efficiency, andpreparation methods thereof. The catalyst is characterized by a highheavy-oil-conversion capacity, moderate coke selectivity, and a highyield of the target product(s).

The present invention provides a new catalytic cracking catalyst withhigh heavy oil conversion efficiency, characterized in that, in thecatalyst composition, there are 2 to 50% by weight of an ultra-stablerare earth type Y molecular sieve, 0.5 to 30% by weight of one or moreother molecular sieves, 0.5 to 70% by weight of clay, 1.0 to 65% byweight of high temperature resistant inorganic oxides, and 0.01 to 12.5%by weight of rare earth oxide; wherein the ultra-stable rare earth typeY molecular sieve means an ultra-stable rare earth type Y molecularsieve having 0.5 to 25% by weight of rare earth oxide, not more than1.2% by weight of sodium oxide, a crystallinity of 40 to 75%, and alattice parameter of 2.449 nm to 2.472 nm. The preparation process forthe ultra-stable rare earth type Y molecular sieve includes a rare-earthexchange and a dispersing pre-exchange, wherein the order of the rareearth exchange and the dispersing pre-exchange is not limited, and therare earth exchange and the dispersing pre-exchange are consecutivelyconducted without a calcination process therebetween. The dispersingpre-exchange refers to a process of adjusting the molecular sieveslurry's concentration to a solid content of 80 to 400 g/L and adding0.2 to 7% by weight of a dispersing agent to carry out dispersingpre-exchange at an exchange temperature of 0 to 100° C. for 0.1 to 1.5h. The dispersing agent in the dispersing pre-exchange process isselected from one or more of sesbania gum powder, boric acid, urea,ethanol, polyacrylamide, acetic acid, oxalic acid, adipic acid, formicacid, hydrochloric acid, nitric acid, citric acid, salicylic acid,tartaric acid, benzoic acid, and starch. No ammonium salt is used in therare earth exchange or the dispersing pre-exchange.

The present invention further provides a preparation method for theheavy oil catalytic cracking catalyst, comprising:

(1) preparation of an ultra-stable rare earth type Y molecular sieve,wherein the raw material, NaY molecular sieve (preferably with asilica-to-alumina ratio of more than 4.0, and a crystallinity of higherthan 70%), is subjected to a rare earth exchange and a dispersingpre-exchange, then the molecular sieve slurry is filtered, washed, andsubjected to a first calcination to afford a “one-exchangeone-calcination” rare earth sodium Y molecular sieve, wherein the orderof the rare earth exchange and the dispersing pre-exchange is notlimited; and the “one-exchange one-calcination” rare earth sodium Ymolecular sieve is then subjected to ammonium exchange for sodiumreduction and a second calcination so as to obtain an ultra-stable rareearth type Y molecular sieve;

(2) preparation of the heavy oil catalyst, wherein the aboveultra-stable rare earth type Y molecular sieve component, clay, and aprecursor of a high temperature resistant inorganic oxide are mixed,homogenized, shaped by spraying, calcinated and washed, to obtain thecatalyst product.

In step (1) of the preparation process of the heavy oil catalyticcracking catalyst according to the present invention, i.e., in theprocess to obtain the ultra-stable rare earth type Y molecular sieve,between the rare earth exchange and the dispersing pre-exchange of theNaY molecular sieve, the molecular sieve slurry may or may not be washedand filtered. During the rare earth exchange, the RE₂O₃/Y zeolite (bymass) is preferably 0.005 to 0.25, most preferably 0.01 to 0.20; theexchange temperature is 0 to 100° C., preferably 60 to 95° C.; theexchange pH is 2.5 to 6.0, preferably 3.5 to 5.5; and the exchange timeis 0.1 to 2 h, preferably 0.3 to 1.5 h. During the dispersingpre-exchange, the amount of the dispersing agent added is 0.2 to 7% byweight, preferably 0.2 to 5% by weight; the exchange temperature is 0 to100° C., preferably 60 to 95° C.; the exchange time is 0.1 to 1.5 h. Themolecular sieve slurry after modification is filtered and washed to givea filter cake, which is then dried by flash evaporation to make thewater content thereof between 30% and 50%, and eventually calcinated toafford the “one-exchange one-calcination” ultra-stable rare earth sodiumY molecular sieve, wherein general conditions may be used for thecalcination, for example, calcination at 350 to 700° C. under 0 to 100%water vapor for 0.3 to 3.5 h, preferably at 450 to 650° C. under 15 to100% water vapor for 0.5 to 2.5 h. The “one-exchange one-calcination”ultra-stable rare earth sodium Y molecular sieve is then subjected to asecond exchange and a second calcination to afford the ultra-stable rareearth type Y molecular sieve according to the present invention, whereinthe second exchange and the second calcination are the ammonium exchangefor sodium reduction and the ultra-stabilization process well known inthe industry of the field, and are not limited in the present invention.

In the “one-exchange one-calcination” process for the ultra-stable rareearth type Y molecular sieve according to the present invention,tank-type exchange, belt-type exchange and/or filter cake exchange maybe employed in the exchange process of the rare earth exchange and thedispersing pre-exchange. The rare earth exchange may be carried out inwhich the rare earth compound solution may be divided into severalportions, provided that the total amount of rare earth is not changed,to undergo tank-type exchange, belt-type exchange and/or filter cakeexchange, i.e., multiple exchanges. Similarly, in the dispersingpre-exchange, the dispersing agent may be divided into several portions,provided that the total amount of the dispersing agent is not changed,to undergo tank-type exchange, belt-type exchange and/or filter cakeexchange. When the rare earth exchange and the dispersing pre-exchangeare multiple exchanges, these two types of exchange may be carried outalternately.

The rare earth compound according to the present invention is rare earthchloride, rare earth nitrate or rare earth sulfate, and preferably rareearth chloride or rare earth nitrate.

The rare earth according to the present invention may be lanthanum-richor cerium-rich rare earth, or may be pure lanthanum or pure cerium.

The dispersing agent in the dispersing pre-exchange process according tothe present invention is selected from one or more of, preferably two ormore of sesbania gum powder, boric acid, urea, ethanol, polyacrylamide,acetic acid, oxalic acid, adipic acid, formic acid, hydrochloric acid,nitric acid, citric acid, salicylic acid, tartaric acid, benzoic acid,and starch.

The other molecular sieves in the composition of the catalyst accordingto the present invention are one or more selected from type Y zeolite, Lzeolite, ZSM-5 zeolite, β zeolite, aluminum phosphate zeolite, Qzeolite, preferably type Y zeolite, ZSM-5 zeolite and β zeolite, orthese zeolite having undergone a conventional physical or chemicalmodification, including HY, USY, REY, REHY, REUSY, H-ZSM-5, and Hβ.

The clay according to the present invention is one or more selected fromkaolin, halloysite, montmorillonite, sepiolite, perlite and the like.The high-temperature-resistant inorganic oxide is one or more selectedfrom Al₂O₃, SiO₂, SiO₂—Al₂O₃, and AlPO₄, and the precursor thereofincludes silica-alumina gel, silica sol, alumina sol, silica-aluminacomposite sol, and pseudoboehmite.

The spraying condition according to the present invention is theconventional operation condition for preparation of cracking catalystsand is not limited in the present invention. The post treatment processis the same as that in the prior art, including catalyst calcination,washing, drying, etc., wherein the calcination is preferably calcinationof a sprayed microsphere sample at 200 to 700° C., preferably 300 to650° C., for 0.05 to 4 h, preferably 0.1 to 3.5 h, and the washingcondition is preferably a water/catalyst weight ratio of 0.5 to 35, awashing temperature of 20 to 100° C., and a period of time of 0.1 to 0.3h.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Specification of Raw Materials Used in Examples

1. NaY molecular sieves: NaY-1 (the silica/alumina ratio: 4.8,crystallinity: 92%), NaY-2 (the silica/alumina ratio: 4.1,crystallinity: 83%), manufactured by Lanzhou Petrochemical Corporation,Catalyst Division.

2. Ultra-stable “one-exchange one-calcination” molecular sieve samples:crystallinity being 60%, sodium oxide being 4.3 m %, manufactured byLanzhou Petrochemical Corporation, Catalyst Division.

3. Rare earth solutions: rare earth chloride (rare earth oxide: 277.5g/L), rare earth nitrate (rare earth oxide: 252 g/L), both of which areindustrial grade and purchased from Lanzhou Petrochemical Corporation.Catalyst Division.

4. Sesbania gum powder, boric acid, urea, ethanol, polyacrylamide,oxalic acid, adipic acid, acetic acid, formic acid, hydrochloric acid,nitric acid, citric acid, salicylic acid, tartaric acid, and starch, allof which are chemically pure; ammonium chloride, ammonium nitrate,ammonium sulfate, and ammonium oxalate, all of which are industrialgrade.

5. Pseudoboehmite (Loss on Ignition: 36.2%), kaolin (Loss on Ignition:16.4%), halloysite (Loss on Ignition: 21.4%), montmorillonite (Loss onIgnition: 15.8%), perlite (Loss on Ignition: 17.6%) (all of which aresolid); alumina sol with an alumina content of 23.0 weight %; silica solwith a silica content of 24.5 weight %, all of which are industrialgrade.

6. REY, REHY, USY, REUSY molecular sieves, all of which are industrialgrade, manufactured by Lanzhou Petrochemical Corporation, CatalystDivision; β zeolite, industrial grade, manufacture by FushunPetrochemical Corporation; H-ZSM-5, industrial grade, manufactured byShanghai Fudan University.

Example 1

To a reaction kettle equipped with a heating mantle, 3000 g NaY-1molecular sieve (dry basis) and a certain amount of deionized water wereconsecutively added and blended into a slurry having a solid content of220 g/L, and 82 g boric acid and 105 g sesbania gum powder were addedthereto. The temperature was raised to 85° C., an exchange reaction wascarried out for 0.5 h under stirring, followed by filtration andwashing, the resultant filter cake was placed in the reaction kettle,and then 1.67 L rare earth chloride was added. The system pH wasadjusted to 4.0, the temperature was elevated to 80° C., and an exchangereaction was carried out for 0.3 h. The resultant filter cake was driedby flash evaporation such that the moisture content thereof was 30% to50%, and was finally calcinated under 70% water vapor at 670° C. for 1.0h to produce a “one-exchange one-calcination” rare earth sodium Y. To areaction kettle equipped with a heating mantle, 500 g of the“one-exchange one-calcination” ultra-stable rare earth sodium Ymolecular sieve (dry basis) and a certain amount of deionized water wereadded to prepare a slurry having a solid content of 120 g/L, to which120 g ammonium sulfate was added. The system pH was adjusted to 4.2, thetemperature was raised to 90° C., and an exchange reaction was carriedout for 0.8 h, followed by filtration and washing. The filter cake wascalcinated under 80% water vapor at 560° C. for 2.5 h to produce theactive component of a rare earth ultra-stable Y molecular sieveaccording to the present invention, designated as Modified MolecularSieve A-1.

To a reaction kettle with water bath heating, 4.381 L water, 1062 gkaolin, 986 g alumina and 63.5 mL HCl were added and thoroughly mixed,and were stirred for 1 hour, followed by consecutive addition of 448 gModified Molecular Sieve A-1, 63 g H-ZSM-5, and 755 g REUSY which werethen thoroughly mixed. 1500 g alumina sol was slowly added for gelation,and was then shaped by spraying. The resultant microspheres werecalcinated at 400° C. for 0.5 hours. 2 kg calcinated microspheres wereweighed, to which 15 kg deionized water was added, followed by washingat 60° C. for 15 min, and were filtered and dried to produce a crackingcatalyst prepared by the present invention, designated as A.

Example 2

In a reaction kettle equipped with a heating mantle, 3000 g NaY-1molecular sieve (dry basis) and a certain amount of deionized water wereconsecutively added and blended into a slurry having a solid content of360 g/L, followed by addition of 0.82 L rare earth nitrate thereto. Thesystem pH was adjusted to 3.3, the temperature was raised to 80° C., andan exchange reaction was carried out for 1.5 h, followed by filtrationand washing. The resultant filter cake was placed in the reactionkettle, to which 202 g polyacrylamide and 30 g salicylic acid were thenadded. The temperature was then elevated to 78° C. for dispersingexchange, and the exchange reaction was carried out for 0.5 h understirring. The resultant filter cake was dried by flash evaporation suchthat the moisture content thereof was 30% to 50%, and was finallycalcinated under 30% water vapor at 630° C. for 1.8 h to produce a“one-exchange one-calcination” rare earth sodium Y. To a reaction kettleequipped with a heating mantle, 500 g of the “one-exchangeone-calcination” ultra-stable rare earth sodium Y molecular sieve (drybasis) and a certain amount of deionized water were added to prepare aslurry having a solid content of 370 g/L, to which 200 g ammoniumsulfate was added. The system pH was adjusted to 3.6, the temperaturewas raised to 90° C., and an exchange reaction was carried out for 1.2h, followed by filtration and washing. The filter cake was calcinatedunder 20% water vapor at 600° C. for 0.5 h to produce the activecomponent of a rare earth ultra-stable Y molecular sieve according tothe present invention, designated as Modified Molecular Sieve B-1.

In a reaction kettle with water bath heating, 4.620 L water, 1024 gkaolin, 971 g pseudoboehmite and 90.8 mL HCl were added and thoroughlymixed, and were stirred for 1 hour, followed by consecutive addition of338 g Modified Molecular Sieve B-1, 129 g 3 zeolite, 806 g REHY whichwere then thoroughly mixed. 1304 g alumina sol was slowly added forgelation, and was then shaped by spraying. The resultant microsphereswere calcinated at 400° C. for 1.0 h. 2 kg calcinated microspheres wereweighed, to which 20 kg deionized water was added and stirred tilluniform, followed by washing at 35° C. for 40 min, and were filtered anddried to produce a cracking catalyst prepared by the present invention,designated as B.

Example 3

To a reaction kettle equipped with a heating mantle, 3000 g NaY-1molecular sieve (dry basis) and a certain amount of deionized water wereconsecutively added and blended into a slurry having a solid content of150 g/L, followed by addition of 43 g HCl thereto. A reaction wascarried out at 85° C. for 1 h, followed by addition of 1.68 L rare earthchloride. The system pH was adjusted to 3.7, the temperature was raisedto 90° C., and an exchange reaction was carried out for 1 h. Themolecular sieve slurry was then filtered and subjected to a belt-typeexchange using a dispersant under the following belt-type exchangeconditions: preparing a pH=3.4 solution with 35 g oxalic acid, raisingthe temperature to 85° C., and the belt-type filter having a degree ofvacuum of 0.04. The resultant filter cake was then dried by flashevaporation such that the moisture content thereof was 30% to 50%, andwas finally calcinated under 10% water vapor at 510° C. for 2.0 h toproduce a “one-exchange one-calcination” rare earth sodium Y. To areaction kettle equipped with a heating mantle, 500 g of the“one-exchange one-calcination” ultra-stable rare earth sodium Ymolecular sieve (dry basis) and deionized water were added to prepare aslurry having a solid content of 145 g/L, to which 80 g ammonium sulfatewas added. The system pH was adjusted to 3.5, the temperature was raisedto 90° C., and an exchange reaction was carried out for 1.2 h, followedby filtration and washing. The filter cake was calcinated under 50%water vapor at 650° C. for 2 h to produce the active component of a rareearth ultra-stable Y molecular sieve according to the present invention,designated as Modified Molecular Sieve C-1.

To a reaction kettle with water bath heating, 4.854 L water, 1125 ghalloysite, 825 g pseudoboehmite and 51.4 mL HCl were added andthoroughly mixed, and were stirred for 1 hour, followed by consecutiveaddition of 406 g Modified Molecular Sieve C-1 and 903 g USY which werethen thoroughly mixed. 1224 g silica sol was slowly added for gelation,and was then shaped by spraying. The resultant microspheres werecalcinated at 600° C. for 0.3 h. 2 kg calcinated microspheres wereweighted, to which 15 kg deionized water was added, followed by washingat 80° C. for 30 min, and were filtered and dried to produce a crackingcatalyst prepared by the present invention, designated as C.

Example 4

To a reaction kettle equipped with a heating mantle, 3000 g NaY-1molecular sieve (dry basis) and a certain amount of deionized water wereconsecutively added and blended into a slurry having a solid content of320 g/L, followed by addition of 30 g nitric acid thereto. Thetemperature was raised to 85° C., and an exchange reaction was carriedout for 0.8 h under stirring, followed by addition of 0.95 L rare earthnitrate. The system pH was adjusted to 3.3, the temperature was raisedto 80° C., and an exchange reaction was carried out for 1.8 h. Finally62 g starch was added, and the reaction was continued at 80° C. for 0.5h, followed by filtration and washing. The resultant filter cake wasdried by flash evaporation such that the moisture content thereof was30% to 50%, and was finally calcinated under 60% water vapor at 560° C.for 2 h to produce a “one-exchange one-calcination” rare earth sodium Y.To a reaction kettle equipped with a heating mantle, 500 g of the“one-exchange one-calcination” ultra-stable rare earth sodium Ymolecular sieve (dry basis) and deionized water were added to prepare aslurry having a solid content of 280 g/L, to which 130 g ammoniumsulfate was added. The system pH was adjusted to 4.0, the temperaturewas raised to 90° C., and an exchange reaction was carried out for 0.5h, followed by filtration and washing. The filter cake was calcinatedunder 60% water vapor at 680° C. for 1 h to produce the active componentof a rare earth ultra-stable Y molecular sieve according to the presentinvention, designated as Modified Molecular Sieve D-1.

To a reaction kettle with water bath heating, 4.577 L water, 1055 gkaolin, 983 g alumina and 63.5 mL HCl were added and thoroughly mixed,and were stirred for 1 hour, followed by consecutive addition of 892 gModified Molecular Sieve D-1, 63 g ZSM-5 zeolite, 118 g USY and 188 gREY which were then thoroughly mixed. 1500 g alumina sol was slowlyadded for gelation, and was then shaped by spraying. The resultantmicrospheres were calcinated at 400° C. for 0.5 hours. 2 kg calcinatedmicrospheres were weighed, to which 10 kg deionized water was added,followed by washing at 40° C. for 20 min, and were filtered and dried toproduce a cracking catalyst prepared by the present invention,designated as D.

Example 5

To a reaction kettle equipped with a heating mantle, 3000 g NaY-1molecular sieve (dry basis) and a certain amount of deionized water wereconsecutively added and blended into a slurry having a solid content of350 g/L. 42 g citric acid and 28 g sesbania gum powder were then addedthereto. The temperature was raised to 82° C., and an exchange reactionwas carried out for 1.3 h under stirring. When the reaction wascompleted, 0.56 L rare earth nitrate was added, and an exchange reactionwas carried out at 85° C. for 0.8 h. Subsequently, the molecular sieveslurry was filtered and subjected to a belt-type exchange under thefollowing belt-type exchange conditions: raising the temperature of therare earth nitrate solution to 88° C., the pH for exchange being 4.7,the rare earth nitrate being added at RE₂O₃/Y zeolite of 0.04, and thebelt-type filter having a degree of vacuum of 0.03. The resultant filtercake was then dried by flash evaporation such that the moisture contentthereof was 30% to 50%, and was finally calcinated under 80% water vaporat 530° C. for 1.5 h to produce a “one-exchange one-calcination” rareearth sodium Y. To a reactor equipped with a heating mantle. 500 g ofthe “one-exchange one-calcination” ultra-stable rare earth sodium Ymolecular sieve (dry basis) and deionized water were added to prepare aslurry having a solid content of 150 g/L, to which 100 g ammoniumsulfate was added. The system pH was adjusted to 4.0, the temperaturewas raised to 90° C., and an exchange reaction was carried out for 1 h,followed by filtration and washing. The filter cake was calcinated under60% water vapor at 620° C. for 2 h to produce the active component of arare earth ultra-stable Y molecular sieve according to the presentinvention, designated as Modified Molecular Sieve E-1.

To a reaction kettle with water bath heating, 6.5 L water, 995 g kaolin,676 g alumina and 130 ml HCl were added and thoroughly mixed, and werestirred for 1 hour, followed by consecutive addition of 558 g ModifiedMolecular Sieve E-1, 19 g H-ZSM-5, and 830 g REUSY which were thenthoroughly mixed. 1359 g alumina sol was slowly added for gelation, andwas then shaped by spraying. The resultant microspheres were calcinatedat 500° C. for 0.6 h. 2 kg calcinated microspheres were weighed, towhich 19 kg deionized water was added, followed by washing at 80° C. for10 min, and were filtered and dried to produce a cracking catalystprepared by the present invention, designated as E.

Comparative Example 1

A REUSY molecular sieve was prepared by the same method as that shown inExample 3, except that HCl and oxalic acid were not added. The resultantultra-stable rare earth type Y molecular sieve is designated as F-1, andthe resultant catalyst is designated as F.

Comparative Example 2

In this comparative example, the molecular sieve preparation methoddescribed in CN200510114495.1 was used in order to examine the reactionperformance of this molecular sieve. The preparation process for thecatalyst was the same as that in Example 5.

3000 g (dry basis) ultra-stable one-exchange one-calcination molecularsieve sample (Na₂O content: 1.4 weight %, RE₂O₃ content: 8.6 weight %,lattice parameter: 2.468 nm, relative crystallinity: 62%) producedhydrothermally by the Catalyst Division of Lanzhou PetrochemicalCorporation was added into a 3 L aqueous solution of 2N oxalic acid, andwas stirred until thoroughly mixed. The temperature was raised to 90 to100° C., and a reaction was carried out for 1 hour, followed byfiltration and washing. The resultant filter cake was placed into 6 Ldeionized water, to which a 1.46 L solution of rare earth nitrate wasadded. The temperature was raised to 90 to 95° C., at which a reactionwas carried out for 1 hour, followed by filtration and washing. Thefilter cake was oven dried at 120° C. to afford the molecular sievesample of this comparative example, designated as H-1.

To a reaction kettle with water bath heating, 6.5 L water, 995 g kaolin,676 g alumina and 130 mL HCl were added and thoroughly mixed, and werestirred for 1 hour, followed by consecutive addition of 558 g ModifiedMolecular Sieve H-1, 19 g H-ZSM-5, and 830 g REUSY which were thenthoroughly mixed. 1359 g alumina sol was slowly added for gelation, andwas then shaped by spraying. The resultant microspheres were calcinatedat 500° C. for 0.6 h. 2 kg calcinated microspheres were weighed, towhich 19 kg deionized water was added, followed by washing at 80° C. for10 min, and were filtered and dried to produce a cracking catalystprepared by the present invention, designated as H.

Comparative Example 3

In this comparative example, the molecular sieve preparation methoddescribed in CN97122039.5 was used, and the preparation process for thecatalyst was the same as that in Example 3.

To a reaction kettle equipped with a heating mantle, deionized water and3000 g (dry basis) NaY-1 molecular sieve were added and blended into aslurry having a solid content of 90 g/L. The temperature was raised to80° C. under stirring, 50 g HCl was added, the temperature wasmaintained for 8 hours, and then a 1.65 L solution of rare earthchloride and 1200 g solid ammonium chloride were added and stirred for 1hour. Filtration and washing were performed until no chloride anion wasdetectable. The resultant wet filter cake (with a water content of 47%)was calcinated at 600° C. for 2 hours to afford the molecular sievesample of this comparative example, designated as G-1.

To a reaction kettle with water bath heating, 4.854 L water, 1125 ghalloysite, 825 g pseudoboehmite and 51.4 mL HCl were added andthoroughly mixed, and were stirred for 1 hour, followed by consecutiveaddition of 406 g Modified Molecular Sieve G-1 and 903 g USY which werethen thoroughly mixed. 1224 g silica sol was slowly added for gelation,and was then shaped by spraying. The resultant microspheres werecalcinated at 600° C. for 0.3 h. 2 kg calcinated microspheres wereweighted, to which 15 kg deionized water was added, followed by washingat 80° C. for 30 min, and were filtered and dried to produce a crackingcatalyst prepared by the present invention, designated as G.

INDUSTRIAL APPLICABILITY

Method for Analysis and Evaluation Used in the Examples

1. Lattice parameter (a₀): X-ray diffraction.

2. Crystallinity (C/C₀): X-ray diffraction.

3. Silica-to-alumina ratio: X-ray diffraction.

4. Na₂O content: flame photometry.

5. RE₂O₃ content: colorimetry.

6. Microreactor activity: samples were pretreated at 800° C. under 100%water vapor for 4 hours. The raw material for the reaction was Daganglight diesel, the reaction temperature was 460° C., the reaction timewas 70 seconds, the catalyst load was 5.0 g, the catalyst/oil weightratio was 3.2, and the overall conversion percentage was taken as themicroreactor activity.

7. ACE heavy oil microreactor: the reaction temperature was 530° C., thecatalyst/oil ratio was 5, and the raw oil was Xinjiang oil blended with30% vacuum residual oil.

The physical and chemical properties of the ultra-stable rare earth typeY molecular sieves prepared in the Examples and Comparative Examples inconnection with the present invention are listed in Table 1. Theanalysis results show that the new molecular sieves are characterized bygood structural stability and a small grain size as compared to those ofthe Comparative Examples.

TABLE 1 Analysis of physical and chemical properties of molecular sievesRare Earth Sodium Lattice Retaining of Collapse Particle size MolecularOxide Oxide Parameter Relative Relative Temperature Distribution μm ItemSieve No. m % m % nm Crystallinity % Crystallinity % ° C. D(v,0.5)D(v,0.9) Examples A-1 15.45 1.1 2.468 51 68.2 1019 2.86 14.59 B-1 6.890.94 2.462 59 72.1 1022 2.75 13.67 C-1 15.54 0.92 2.469 51 70.2 10182.92 17.26 D-1 7.98 1.05 2.461 57 70.3 1025 2.92 15.92 E-1 8.70 0.862.461 55 68.8 1017 2.65 13.67 Comparative F-1 6.78 1.1 2.464 52 51.2 9984.23 33.58 Examples H-1 8.27 1.60 2.467 54 54.5 1002 4.83 37.42 G-112.86 1.82 2.468 49 56.3 1000 4.85 41.48

The results of evaluation of the reaction performance of the catalystsprepared in Examples 1 to 5 and the Comparative Examples are listed inTable 2.

TABLE 2 Evaluation results for the microreactor activity of ACE heavyoil Catalyst No. A B C D E F H G Molecular sieves A-1 B-1 C-1 D-1 E-1F-1 H-1 G-1 Mass balance Dry gas 2.67 2.68 2.67 2.67 2.69 2.81 2.90 2.84m % Liquified gas 22.54 22.40 22.36 22.37 22.64 23.26 23.59 23.22Gasoline 54.15 54.07 54.17 54.18 53.67 52.92 52.84 53.22 Diesel 10.4610.56 10.54 10.50 10.59 9.82 9.69 9.99 Heavy oil 3.58 3.59 3.61 3.643.70 4.31 3.94 4.11 Coke 6.60 6.71 6.65 6.64 6.71 6.88 7.05 6.61 Total100 100 100 100 100 100 100 100 Conversion, m % 85.96 85.86 85.84 85.8685.71 85.87 86.38 85.90 Total liquid yield, m % 87.15 87.03 87.07 87.0586.89 86.00 86.11 86.44 Light oil yield, m % 64.61 64.63 64.71 64.6864.25 62.75 62.52 63.21

From the evaluation results about the microreactor activity of ACE heavyoil, it can be seen that the catalysts prepared by the methods accordingto the present invention have superior heavy-oil-conversion capacity andcoke selectivity as compared to comparative catalysts, and also have atotal liquid yield and a light oil yield much higher than those of thecomparative catalysts. Table 4 shows the evaluation results of acatalyst B riser. As compared to catalyst C, the total liquid yield ofthe catalyst of the present invention is increased by 0.97%, and thelight oil yield thereof is increased by 0.77%, while the gasolineproperties are similar.

TABLE 4 Evaluation results of a catalyst riser Comparative InventiveCatalysts catalyst G catalyst Mass balance, Dry gas (H2-C2) 1.05 1.17 ω% Liquified gas (C3-C4) 17.95 18.16 Gasoline (C5-204° C.) 50.20 50.44Diesel (204° C.-350° C.) 16.58 17.12 Heavy oil (>350° C.) 6.54 5.55 Coke7.36 7.30 Loss 0.30 0.27 Selectivity Conversion 76.87 77.33 ω % Lightoil yield 66.79 67.56 Total liquid yield 84.74 85.71 Gasoline Normalalkanes 4.48 4.34 composition Isoalkanes 23.75 24.50 ω % Gasolineolefins 45.05 44.00 Cycloalkanes 9.97 10.01 Aromatic hydrocarbons 16.7517.15 Gasoline MON 83.40 83.42 Gasoline RON 93.69 93.82

One of the major active components of the novel heavy oil catalystaccording to the present invention is a rare earth ultra-stable type Ymolecular sieve having high cracking activity stability. In the processof preparing this molecular sieve by rare earth modification, adispersing agent is used to pre-disperse NaY molecular sieves, therebylowering the degree of agglomeration of molecular sieve particles,allowing more molecular sieve surface to be in contact with rare earthions, and reducing the hindrance to rare earth ion exchange. As aresult, more rare earth ions are exchanged into molecular sieve cagesand then migrate into sodalite cages in the subsequent water-vaporcalcination process, and the structural stability and activity stabilityof the molecular sieve are improved. As rare earth ions are located insodalite cages, there are no rare earth ions present in super-cages oron the surface, thereby reducing the acidic intensity and density inthese areas, lowering the coking probability in these active sites, andsatisfactorily resolving the conflict between the heavy oil conversioncapacity and the coke selectivity of the catalyst.

What is claimed is:
 1. A heavy oil catalytic cracking catalyst,characterized in that the catalyst comprises 2% to 50% by weight of anultra-stable rare earth type Y molecular sieve, 0.5% to 30% by weight ofone or more other molecular sieves, 0.5% to 70% by weight of clay, 1.0%to 65% by weight of high-temperature resistant inorganic oxides, and0.01% to 12.5% by weight of rare earth oxide; wherein the ultra-stablerare earth type Y molecular sieve is an ultra-stable rare earth type Ymolecular sieve having 0.5% to 25% by weight of rare earth oxide, notmore than 1.2% by weight of sodium oxide, a crystallinity of 40% to 75%,and a lattice parameter of 2.449 nm to 2.472 nm; and wherein theultra-stable rare earth type Y molecular sieve is prepared from a NaYmolecular sieve as a raw material by a preparation method in which amolecular sieve slurry of the raw material is subjected to a rare earthexchange and a dispersing pre-exchange, then the molecular sieve slurryis further filtered, washed, and subjected to a first calcination toproduce an intermediate rare earth sodium Y molecular sieve, wherein theorder of the rare earth exchange and the dispersing pre-exchange stepsis not limited, the rare earth exchange and the dispersing pre-exchangebeing consecutively conducted without a calcination processtherebetween, and the intermediate rare earth sodium Y molecular sievethen being subjected to an ammonium salt exchange for sodium reductionand a second calcination so as to obtain an ultra-stable rare earth typeY molecular sieve; wherein the dispersing pre-exchange refers to aprocess of adjusting the molecular sieve slurry's concentration to asolid content of 80 to 400 g/L and adding 0.2% to 7% by weight of adispersing agent to carry out dispersing pre-exchange at an exchangetemperature of 0° C. to 100° C. for 0.1 to 1.5 h; wherein the dispersingagent in the dispersing pre-exchange process is selected from one ormore of sesbania gum powder, boric acid, urea, ethanol, polyacrylamide,acetic acid, oxalic acid, adipic acid, formic acid, hydrochloric acid,nitric acid, citric acid, salicylic acid, tartaric acid, benzoic acid,and starch; and wherein no ammonium salt is used in the rare earthexchange or the dispersing pre-exchange.
 2. The catalyst according toclaim 1, characterized in that the other molecular sieves are selectedfrom one or more of type Y zeolite, L zeolite, ZSM-5 zeolite, β zeolite,aluminum phosphate zeolite, or Ω zeolite.
 3. The catalyst according toclaim 1, characterized in that the other molecular sieves are one ormore of HY, USY, REY, REHY, REUSY, H-ZSM-5, and β zeolite.
 4. Thecatalyst according to claim 1, characterized in that the clay isselected from one or more of kaolin, halloysite, montmorillonite,sepiolite, and perlite.
 5. The catalyst according to claim 1,characterized in that the high-temperature-resistant inorganic oxide isselected from one or more of Al₂O₃, SiO₂, SiO₂—Al₂O₃, and AlPO₄.
 6. Thecatalyst according to claim 1, characterized in that the preparationprocess further comprises: preparation of the heavy oil catalyst,wherein the ultra-stable rare earth type Y molecular sieve, one or moreother molecular sieves, clay, and a precursor of a high-temperatureresistant inorganic oxide are mixed, homogenized, shaped by spraying,calcinated and washed, to obtain the heavy oil catalyst product.
 7. Thecatalyst according to claim 1, characterized in that during the rareearth exchange, the mass ratio RE₂O₃/Y zeolite is 0.005 to 0.25, theexchange temperature is 0° C. to 100° C., the exchange pH is 2.5 to 6.0,and the exchange time is 0.1 to 2 h.
 8. The catalyst according to claim1, characterized in that during the rare earth exchange, the mass ratioRE₂O₃/Y zeolite is 0.01 to 0.20, the exchange temperature is 60° C. to95° C., exchange pH is 3.5 to 5.5, and the exchange time is 0.3 to 1.5h; and during the dispersing pre-exchange, the amount of the dispersingagent added is 0.2% to 5% by weight, the exchange temperature is 60° C.to 95° C., and the exchange time is 0.1 to 1.5 h.
 9. The catalystaccording to claim 1, characterized in that, between the rare earthexchange and the dispersing pre-exchange, the molecular sieve slurry iswashed and filtered.
 10. The catalyst according to claim 1,characterized in that tank-type exchange, belt-type exchange and/orfilter cake exchange is employed for the exchange process of the rareearth exchange or the dispersing pre-exchange.
 11. The catalystaccording to claim 1, characterized in that, in the process of the rareearth exchange, a rare earth compound solution is divided into multipleportions for multiple exchanges, and each of the multiple exchanges is atank-type exchange, a belt-type exchange and/or a filter cake exchange.12. The catalyst according to claim 1, characterized in that, in theprocess of the dispersing pre-exchange, the dispersing agent is dividedinto multiple portions for multiple exchanges, and each of the multipleexchanges is a tank-type exchange, a belt-type exchange and/or a filtercake exchange.
 13. The catalyst according to claim 1, characterized inthat the rare earth exchange and the dispersing pre-exchange are carriedout alternately multiple times.
 14. The catalyst according to claim 1,characterized in that the calcination condition for the firstcalcination of the molecular sieve is calcination at 350° C. to 700° C.under 0 to 100% water vapor for 0.3 to 3.5 h.
 15. The catalyst accordingto claim 6, characterized in that the precursor of thehigh-temperature-resistant inorganic oxide is selected from the groupconsisting of silica-alumina gel, silica sol, alumina sol,silica-alumina composite sol, and pseudoboehmite.
 16. The catalystaccording to claim 11, characterized in that the rare earth compound israre earth chloride, rare earth nitrate or rare earth sulfate.
 17. Thecatalyst according to claim 16, wherein the rare earth in the rare earthcompound is lanthanum-rich rare earth, cerium-rich rare earth, purelanthanum or pure cerium.
 18. The catalyst according to claim 1,characterized in that the calcination condition for the secondcalcination is calcination at 200° C. to 700° C. for 0.05 to 4 hours.19. The catalyst according to claim 6, characterized in that thecalcination condition is calcination at 300° C. to 650° C. for 0.1 to3.5 hours.
 20. The catalyst according to claim 6, characterized in thatthe washing conditions are as follows: the weight ratio water/catalystis 0.5 to 35, the washing temperature is 20° C. to 100° C., and thewashing duration is 0.1 to 0.3 hours.